Electric translation circuit



Feb. 20, 1940. G. GUANELLA 2,191,315

ELECTRIC TRANSLATION CIRCUIT Filed Nov. 1, 1938 2SheetsSheet l a of J ZI 0c EIT IMPEDANCE T Z K 15 T (MPEDANCE T 2 INVENTOR. qusi'awfluanellaATTORNEY.

Patented Feb. 20, 1940 UNITED STATES ELECTRIC TRANSLATION CIRCUITGustave Guanella, Zurich, Switzerland, assignor to Radio PatentsCorporation, a corporation of New York Application November 1, 1938,Serial No. 238,127 In Switzerland November 25, 1937 11 Claims.

The present invention relates to electric circuits or networks and moreparticularly to arrangements for and a method of controlling thepropagation factor or coupling coefllcient of such circuits or networksin dependance upon a controlling current or potential.

A further object of the invention is the provision in a translationcircuit of means for and a method of controlling the phase rotation of acurrent or potential impressed upon such circuit in dependance uponvariations of a controlling electric current or potential.

The problem of controlling the coupling effected by electrical circuitsor networks in dependence upon a controlling current or potential arisesin many cases in communication and high frequency engineering systems.Thus, it is often required to vary the amplitude relation between theinput and output potentials of a tor of a coupling or translatingcircuit or net' work is suited for various purposes, more particularlyif it is desired to control the amplitude relation and/or the phaserotation of alternating currents or potentials rapidly or slowly inaccordance with variations of a controlling potential.

It is well known to adjust the transmitting characteristics of a networkor circuit purely electrically by the employment of electron tubes ascoupling elements having a curved operating characteristic and byvarying the average grid bias potential or potential of a specialauxiliary grid or other control electrode.

it has furthermore been proposed to effect a coupling variation purelyelectrically by the employment of iron cored induction coils as couplingelements provided with a special magnetizing control winding energizedby the controlling current.

According to the present invention, it is proposed to employ devices ina translation circuit having mechanically fixed electrodes whichelectrodes in conjunction with a suitable intermediate layer disposedtherebetween form a condenser the capacity of which can be varied by apotential impressed upon the electrodes in such a manner that a certainvariation of the applied biasing potential causes a correspondingvariation of the coupling or propagation factor of the circuit'ornetwork without essentially affecting the frequency or tuningcharacteristics of the circuit.

Such condensers which are also described in my copending U. S.application, Serial, No. 201,945, filed April 14, 1938, include a verythin blocking layer embedded between suitable electrodes in such amanner that the capacity for the frequencies to be dealt with isdependent upon an applied biasing potential and the loss angle of thecondenser does not exceed about 45". Since this thin blocking layer oflow electrical conductivity which in general does not have a thicknessgreater than 10- cm. constitutes an essential element of variablepotential controlled condensers of this type and in many respectsresembles the construction and arrangement of the known blocking layeror dry rectifiers, potential controlled or biased condensers of thistype will be referred to as blocking layer condensers for the purpose ofthis specification.

As pointed out in the above copending application, no fully satisfactoryphysical explanation has been found for the behavior and characteristicsof these blocking layer condensers. However, extensive practicalexperiments made by applicant have shown that by using a sulficientlythin intermediate or blocking layer embedded between the electrodes ofsuitable composition and characteristics substantial capacity variationscan be realized. This phenomenon for instance may be demonstrated withmost of the known dry rectifiers such as selenium rectifiers, cuprousoxide rectiflers, by applying the controlling potential in the currentblocking direction of the rectifier. A capacity variation has also beenfound to be present in the less common rectifier combinations such asuranium dioxide rectifiers, zinc dioxide rectifiers, and others. Theblocking layer between the electrodes may consist of a suitableinsulating material applied or formed in any suitable manner upon theelectrodes such as a suiilciently thin layer of organic lacquers appliedto a conducting or semi-conducting electrode. It was found furthermorethat the capacity variations are dependent upon the nature orcomposition of the adjoining electrodes, the kind of contact and thetransition or boundary zone between the blocking layer proper and theadjoining electrodes.

. The above phenomenon has also been observed in dry or electrolyticcondensers. Substantial capacity variations have been obtained witharrangements containing tungsten, niobium, or tantalum as anode materialand placed in a suitable electrolyte. The blocking layer in suchelectrolytic devices is produced by electrolytic formation between theelectrolyte and the metal. In addition to the capacity variations indevices of the latter type, there is in most cases present a very slowaction of the biasing potential resulting in a variable formationdepending on the magnitude of the control potential.

As will be understood, the biasing potential applied to blocking layercondensers of the above described type should be varied only to such anextent as to maintain the loss angle within the permissible limits toprevent undesirable distortion of the alternating current potentials tobe translated due to incidental rectification and also to prevent thedirect current from assuming excessive values. In devices which pass theelectric current in one direction only such as dry electrolyticrectifiers, it is therefore not generally necessary to operate withbiasing potential applied in the blocking direction.

According to the present invention, blocking layer condensers of theabove type are connected suitably in electrical networks of both simpleand cbmplex construction in such a manner that the variations of thecapacity eflected by an applied controlling or biasing current isadaptedto vary the propagation factor or coupling characteristics of thecircuit or network in a desired manner without substantially interferingwith the tuning of frequency characteristics of the.

circuit.

Further details and aspects of the invention will become more apparentfrom the following detailed description taken with reference to theaccompanying drawings forming part of this specification, and whereinFigures 1 to 3 illustrate schematically simple networks or four-polecircuits adapted for practising the invention, a

Figure 3a is a graph illustrating the variation of the capacity andresistance of a blocking layer condenser in dependance upon the appliedbias or control potential,

Figure 4 illustrates a simple potentiometer. circuit with a variableblocking layer condenser embodied therein according to the invention,

Figure 5 is a modification of Figure 4 embodying two blocking layercondensers controlled by a common biasing battery,

Figures 6 and 7 are bridge type transmission networks embodyingcontrollable blocking layer condensers according to the invention,

Figure 8 is a network illustrating the employment of the invention foreffecting a variable phase rotation between input and output potentialin dependance upon a controlling or biasing electric current,

Figure 9 illustrates an embodiment of the invention for effecting acurrent limitation in a translating circuit,

Figure 10 is a further exemplification of an arrangement embodyingpotential controlled condensers for efiecting automatic expansion orcontraction of the intensity range of signals or potentials to betranslated,

Figures 11 and 12 illustrate substitute or limiting networks to be usedin connection with the remaining figures, and

Figure 13 represents an amplifying circuit utilizing potentialcontrolled condensers according to the invention in place of amplifyingtubes.

Similar reference characters identify similar parts throughout thedifferent views of the drawings. a Referring to Figure 1, there isillustrated a four-pole network known as a T-circuit having a pair ofinput terminals a, b and a pair of output terminals 0, d. A pair ofimpedances Z1, Z: are serially connected between the terminals a and 0while a further impedanceZ: is connected between the junction of theimpedances Z1 and Zr and the remaining input and output terminals b and11, respectively. An input potential E1 impressed upon the terminals a,b will be translated through the circuit and an output potential E2. isderived from the terminal c, 07.

Figure 2 shows a general network or four-pole circuit known as aw-circuit wherein the impedances Z1 and Z: are connected across theinput and output terminals, respectively, and the impedance Z: isarranged between the input terminal a and the output terminal c in amanner well known.

Figure 3 shows a translation network of the Wheatstone bridge typecomprising four bridge arms formed by impedances Z1 to Z4 with the inputterminals a, b connected to one pair of apices of the bridge and theoutput terminals 0, 41 connected to the remaining pair of apices of thebridge circuit.

The impedances Z are so-called two-pole circuits or networks and shouldnot contain any resonating elements forming resonant systems likely tointerfere with the control of the transmission characteristics orpropagation factor in accordance with the invention. By varying one ofthe impedances Z it is possible in a known manner to control the ratiobetween the input and output potentials E1 and E2, or in other words thepropagation or translation factor of the circuit or network.

According to the present invention, at least one orseveral of theimpedances Z include one or more blocking layer condensers which ifdesired may be operatively associated with other circuit elements insuch a maner that the propagation factor of the network may be variedwithin predetermined limits by the controlling or biasing potential.

Referring to Figure 311 there is shown a graph illustrating thevariations of the capacity C and the internal resistance Rv of ablocking layer condenser in dependance upon a biasing or controllingpotential e applied thereto in the current blocking direction. Such acondenser may be e. g. of the oxide type comprising a base electrode(negative electrode) coated with an oxide layer formed thereon in anysuitable manner and a covering electrode (positive electrode) in contactwith the oxide or blocking layer such as a plate or disc pressed againstthe blocking layer by a spring or the like. As is seen fromthis graphwhich represents the results obtained from a large number of experimentsconducted by applicant, the capacity of a blocking layer condenserdecreases as the biasing potential is increased while the internalresistance varies in the opposite direction.

Referring to Figure 4, there is shown a simple potentiometer circuit fortranslating an input potential E1 comprising an impedance Z and ablocking layer condenser K in series and connected across the inputterminals 0., b. In the for instance if a constant input and outputreexample shown the output potential Es is derived from the voltage dropdeveloped across the im pedance Z connected to the output terminal c, d.In a simple potentiometer circuit oi this type the voltage ratio 5 E1with no load connected to the output is equal to whereby Zx representsthe impedance of the blocking layer condenser K. By varying the capacity0! the latter according to an impressed controlling potential it is seenthat the voltage transmitting ratio of the circuit can be varied in adesired manner. This transmitting ratio in general is or a complexnature; that is, it includes a phase rotation of the output potential E1relative to the input potential E1. The phase rotation may be avoided inpractice if Z constitutes a capacity having a loss angle correspondingto the average loss angle of the blocking layer condenser K. i This canbe realized by the provision of a resistance in series with the blockinglayer condenser as shown in Figure 12. The blocking layer condenser Kand impedance Z may be mutually exchanged without essentially aflectingthe operation of the circuit, as is understood.

In place of the impedance Z in Figure 4, it is possible to provide afurther blocking layer condenser such as shown in the embodimentaccording to Figure 5. In the latter, two blocking layer condensers K1and K: are connected in series in the same sense as regards theircurrent passing directions and placed across the input terminals a, 17through a coupling or blocking condenser 01., while the output potentialis derived from the potential drop developed across the condenser K:through a further coupling or blocking condenser C2. The bias or controlpotential is supplied by a battery B connected across both condensers inseries with an induction or choke coil I1. In this arrangement bothcondensers K1 and K2 are controlled diiferentially by the connectionfrom the common junction point thereof to a variable tap t of thebattery B, said connection including a further choke coil Is. In therepresentation of the blocking layer condenser in the drawing, the thinline represents the negative electrode, the thick line represents thepositive electrode, while the dashed line represents the blocking layerembedded between the electrodes.

It is thus seen that in Figure 5 both condensers are biased in theblocking direction and that the bias may be controlled differentially byadjusting the tap t or any equivalent potential supply means such as apotentiometer resistance as will be understood by those skilled in theart. The condensers C1 and C: serve to block the biasing potential fromthe input and output circuits while the choke coils I1 and I: areprovided to prevent a short circuit of the alternating currentpotentials through the direct current control cir cuits. As pointed out,by varying the tap t of the battery B the capacities of the blockinglayer condensers K1 and K2 vary in opposite directions, therebyeffecting a variation of the amplitude of the output potential E2 inrelation to a given amplitude of the input potential E1.

Potentiometer circuits according to Figures 4 and 5 derived from Figure1 by omission of the impedance Z2 in many cases are unsuited to fullycomply with the practical requirements. Thus sistance is required thenetwork: should comprise at least three two-pole elements such as shownin Figures 1 to 8.

On the other hand, arrangements based on a Wheatstone bridge accordingto Figure 3 are to be preferred in cases when coupling variations aredesired down to a complete decoupling between the input and outputcircuits.

An arrangement adapted for this latter purpose is shown in Figure 6. Thelatter represents a 'Wheatstone bridge comprising two arms formed 'byimpedances Z1 and Z: and a pair of further arms formed by blocking layercondensers K1 and K: each in series with a biasing battery B1 and B1,

respectively. The batteries B1 and B2 provide a steady or constantbiasing potential in the blocking direction (e0 according to Figure 3a).The controlling potential e which may be derived from any suitablesource such as a battery with associate potentiometer, a microphone orany other varying potential source is impressed through terminals r, 3across the input terminals a, b or upper and lower apices of the bridgecircuit in series with a pair of choke cells 11 and In. The impedancesZ1 and Z: may consist of induction coils, resistors, condenser, or acombination of these elements. If condensers are used they should beshunted by an impedance passing direct current such as a resistance toprovide a conductive current path for the control potential e to theblocking layer condensers K1 and K2, respectively. The steady biaspotentials provided by the bat--- teries B1 and B2 are such as tonormally produce a balance of the bridge circuit. The blocking layercondensers K1 and K: are then controlled differentially by the variableor alternating control potential e applied to terminals 7', 3, therebyupsetting the balance of the bridge circuit. Thus, if the amplitude ofthe input potential E1 is kept constant it is possible in this manner tovary the amplitude of the output potential E: between zero (balancecondition) and a limit value. In place of the two impedances Z1 and Z;in Figure 6, it is possible to provide in certain cases an inductioncoil with a center tap the inductance of which is suificiently high toavoid resonance effects in conjunction with the condensers K1 and K2.

As pointed out hereinbeiore, the potential controlled condensers K1 andK2 in general require, although not necessarily, a definite zero or biaspotential acting in the blocking direction, specially in the case ofdevices of the type constructed in accordance with the known dryrectiflers. For this purpose the batteries B1 and B2 are provided toproduce a fixed bias or operating point so as seen from Figure 3a. Inplace of separate batteries it is also possible to provide avoltagesource in series with an alternating current blocking impedancesuch as an inductance connected across the output terminals 0, oi.

If it is desired to maintain the input and output potential symmetricalwith respect to a predetermined reference or zero potential such asground, arrangements of the type shown in Figure 7 may be employed. Inthe latter, the input terminals a, b are shunted by an impedance passingdirect current such as an inductance or a resistance R1 provided in theexample shown, choke coils i1 and is being arranged in the connectingleads from the terminals a, b for the purpose pointed out hereafter.Similarly the output terminals 0, d are shunted by a resistance R2. Theupper ends of the resistances R1 and R2 are connected through a blockinglayer condenser K1 in series with a biasing battery R1, and similarlythe lower ends of the resistances R1 and R: are connected through ablocking layer condenser 1Q in series with a biasing battery Ba. Thereare provided a further pair of blocking layer condensers K: and K4 inseries with biasing sources B2 and B4, respectively, and connectedbetween the lower end of resistance R1 and the upper end or resistanceR2 on the one hand, and the upper end of resistance R1 and the lower endof resistance R: on the other hand. The input or control terminals r, sare connected to the center tap points of the resistances R1 and R2. Iffor a certain control potential such as zero control potential thecapacities of all four blocking layer condensers are equal to eachother, the output potential E: for any given amplitude oi the input Ipotential E2 will also be zero. With increasing control potential thebalance of the bridge will be disturbed and the amplitude of the outputpotential increased accordingly.

According to a modification of Figure 7, the control potential e may beimpressed across the output terminals 0, d and the output potential E2derived from the terminals 1', s without ailecting the operation or thesystem as is obvious in view of the symmetry of the circuit arrangement.

It will be obvious from the above that the blocking layer condensers inFigure 7 in addition to the controlling potential should in general bebiased in the blocking direction by a certain steady potential (eoaccording to Figure 3a) in order s to prevent the direct potentialthrough the condensers from exceeding a permissible limit. The steadybiasing potentials are provided in Figure 7 by the batteries B1 to B4.In special cases the steady biasing potential may be applied in adifferent manner. According to a simple arrangement the steady biasingpotential may be supplied together with the control potentialsuperimposed thereon such as by replacing the condensers m andK4 or thecondensers K1 and K: by fixed condensers having a capacity and lossangle corresponding to the respective average values of K1 and K! or K:and K4,

v respectively, if necessary by the provision of additional substituteelements as shown in Figures 11 and 12. In this case thecontrolling-potential e varies within such limits as to act always inthe blocking direction of the two remaining blocking layer condensers K1and K1 or K: and K4, respectively, thereby dispensing with additionalcurrent sources.

Many of the circuits for eflecting coupling variations by the aid ofblocking layer condensers resemble the known circuit arrangement formutually modulating alternating currents. Thus, for instance the circuitaccording to Figure 7 may be converted into a known ring modulatingcircuit by substituting rectifiers for the blocking layer condensers andby omititng the special steady bias potentials. 0n the other hand, it ispossible to convert the known modulating circuits into arrangements forcoupling controlby substituting blocking layer condensers for thenon-linear resistances or rectifiers used in the former. The basicdifference however in all cases is the fact that in the known modulatingcircuits circuit elements such as dry or vacuum tube rectifiers areemployed whose alternating current resistance is dependent upon a.biasing potential according to a nonlinear relationship, while in thecase of arrangements according to the invention for coupling controlthere are employed condensers having a loss angle not exceeding 45' andbeing capable of control by a variable potential impressed thereon. Inthis manner it is possible to eflect a variable coupling withoutappreciable electric losses in the circuit.

The employment of blocking layer condensers in many cases may result ina substantial capacitive load imposed upon the associate circuits. Thusin the case of an arrangement according to Figure 7 the internalapparent impedance at the input terminals a, b is equal to the averagecapacity of a single blocking layer condenser. The controlling potentiale does not materially eflect this input impedance. If it is desired totransmit a definite frequency or a small band of frequencies theinternal capacity may be compensated by a properly designed inductancethereby leaving only a resistance caused by ohmic losses. Thisinductance is preferably connected in parallel to the input terminals a,b and designed in such a manner as to become resonant to the frequencyof the input potential together with the average capacity of one of theblocking condensers. It is further possible for this purpose to providean inductance having a center tap in place of a resistance R1 designedin such a manner as to result in the desired compensation of theinternal capacity of the circuit.

In many cases it is furthermore desirable to provide the compensatinginductance in series with the input terminals in place of a parallelinductance mentioned, whereby the input current passes through thecompensating inductance. For matters of symmetry in an arrangement ofthe type as shown in Figure 7 it is advantageous to provide the seriesinductance in the form of two windings i1 and is each connected inseries with one of the input leads. In an analagous manner asubstantially constant input capacity may be compensated by one or moreseries or parallel inductances in the remaining circuits shown. 1

In the foregoing circuit arrangements have been shown and describedembodying blocking layer condensers and enabling a control 01' theamplitude ratio or propagation factor purely electrically in accordancewith a variable control potential. In many cases it is required toeffect a variable phase rotation of the transmitted alternatingpotential in accordance with a controlling potential. This object can berealized according to the present invention by the aid of specialcircuits, an exempliflcation of which is shown in Figure 8. The phaseshifting circuit as shown in the latter is of the Wheatstone bridge typecomprising two impedances such as resistances R1 and R2 shown in theexample illustrated and forming two opposite arms 01' the bridge circuitand a pair of blocking layer condensers K1 and K2 forming the remainingbridge arms. The input terminals a, b are connected to one pair ofapices of the bridge and the output terminals 0, d are connected to theremaining pair of apices of the bridge while the controlling potential eis impressed in the example shown across the input in series with chokecoils .I1 and Is in a manner substantially similar to Figure 4. Theapparent reactive impedances of the blocking condensers K1 and K: for acertain bias potential are designed to be equal to the ohmic resistancesR1 and R2. In this case the output potential E2 is phase rotatedrelative to the input potential E1 by not considering any additionalincidental phase shift due to the loss resistances of K1 and K: and theload connected to the output terminals 0, d. This phase rotation may beincreased or decreased by a corresponding variation of the capacities ofthe blocking layer condensers; that is, in accordance with thecontrolling potential e causing an unbalance of the bridge circuit. Asis understood the blocking layer condensers K1 and K: may be properlybiased in the blocking condensers by batteries or in any othersuitablemanner as described hereinbefore.

From the foregoing it will be obvious that any other known type of phaseshifting circuit employing condensers in conjunction with resistors orother impedances may have embodied therein one or more variable blockinglayer condensers with means for electrically controlling the same toeifect a variable phase shift in accordance with the invention. It isunderstood that the circuit according to Figure 8 may serve forcontrolling the propagation factor or input-output amplitude ratio byreplacing the resistances R1 and-R1 by corresponding condensers bridgedby resistors to complete the direct current control circuit.

In the preceding embodiments the control potential is derived from aseparate source and impressed from the outside upon the network whosetransmission characteristics are to be controlled. According to afurther embodiment of the invention the control potential may begenerated within the circuit or network in dependence upon theamplitude, frequency, phase, or any'other characteristic of the energybeing transmitted for obtaining special effects and results as will befurther understood from the following.

Referring to Figure 9, there is illustrated an embodiment for limitingthe ampltude of an alternatng current to a predetermined value. An

.ductance I is connected across the input termore connected to theoutput terminal through a fixed condenser C while a blocking layercondenser K is connected between the lower end of the inductance I andthe right hand terminal of the condenser C or the output terminal 0. Thecondenser C is so designed as to have a capacity corresponding to apredetermined limit capacity of the blocking layer condenser K when amaximum control potential is applied to the latter. Preferably thecondenser C has connected therewith a resistance corresponding to theloss resistance of the condenser K such as a shunt resistance R as shownin Figure 11 or by providing both shunt and series resistances R1 and R2or R1" and R2", respectively, as shown by the substitute networksaccording to Figures 12a and 12b. In this case the bridge will bebalanced or in other words the output circuit will be completelydecoupled from the input circuit in such a manner that the outputpotential E2 will be zero independently of the magnitude of the inputpotential E1. There is further provided a rectifier G connected acrossthe output terminals 0, d shunted by an impedance W1 in series with afixed condenser C. The rectifier G will charge the condenser C throughthe resistance W1 to a potential depending upon the amplitude of theoutput alternating potential E2. Thus, the rectified potential themagnitude of which is proportional to the output potential E2 isimpressed upon the blocking layer condenser K through the lower half ofthe inductance I. If the amplitude of the output potential E1 is low,

the rectified control potential is small; that is, the capacity of Kwill deviate substantially from the capacity of C resulting in a". tightcoupling of the output circuit with the input circuit. If the amplitudeof the output potential increases the two capacities C and K will becomemore and more alike; that is, the coupling will decrease in such amanner as tocounteract the increase of the amplitude of E2 beyond apredetermined limit. Thus, if the amplitude of the input potential E1 issubject to substantial variations it is possible in this manner tomaintain the amplitude of the output potential E2 at a predeterminedsubstantially constant value.

In the arrangement according to Figure 9 the control is retroactive;that is, the rectified potential controlling the blocking condenser isderived from the output of the circuit, or the propagation factor orcoupling is governed by the output of the circuit. As is understood itis also possible to employ a forward control in which case theregulation is effected in dependance upon the input such as amplitude,phase, etc., of the input potential. Aitematively, the arrangement maybe designed and adjusted so as to automatically prevent excessiveamplitude differences in which case an increasing control potentialapplied to the condenser K will cause a gradually increasing unbalanceoi the bridge system.

Moreover, it is possible in special cases for automatic amplitudecontrol to dispense with a special rectifier. An arrangement of thistype is shown in Figure 10. In the latter, two blocking layer condensersK1 and K2 arranged serially in opposition are connected across the inputterminals a, b in potentiometer fashion in series with an impedance Zand are furthermore shunted by serially connected inductances I1, I11with condensers C and C inserted in the opposite connecting leads forthe inductances I1 and I1. The junction point of the condensers K1 andK2 is connected to the common preferably variable point of theinductances I1 and I2 forming a variable voltage divider. In anarrangement of this type an increase of the amplitude of the outputpotential, E2 will cause a charging of the condensers K1 and K: on theone hand and of the comparatively large fixed condensers C and C, on theother hand. This charging potential is equal to one half of the peakvalue of the output potential E2. As a result the series capacity of theblocking layer condensers K1 and K1 will be decreased in such a mannerthat the voltage drop through the impedance Z will be decreased. In thismanner the amplitude ratio increases with increasing output potentialresulting in an increase or expansion of the intensity range of thepotentials or signals translated by the system.- In special cases thecondensers C and C and the ohmic or inductive impedances I1 and I: maybe dispensed with in view of the fact that the average charge of thecondensers K1 and K11 may be sufficient to effect the necessary capacityvariation. As is understood the reverse eifect; that is, a compressionof the intensity range may be realized in an analogous manner by acircuit as shown.

When dealing with alternating potentials of high amplitude, anincidental rectifying efl'ect of the blocking layer condensers mayresult in an undesired charge of these condensers interfering with thevariations of the capacity by an impressed or internally generatedcontrolling potential. Furthermore, non-linear distortions may occur inaddition to other drawbacks and defects. According to a further featureof the invention means are provided to prevent the alternatingpotentials impressed upon the blocking layer condensers from exceeding aprede: termined limit amplitude. This object can be obtained forinstance by connecting several blocking layer condensers in'series orbyproviding a fixed condenser of sufficiently small capacity in serieswith a blocking layer condenser, which fixed condenser if desiredmay beshunted by a parallel resistance to form a path for the direct controlpotential for the blocking layer condensers. A two-pole substitutenetwork of this type is shown in Figure 11 wherein a fixed condenser Cshunted by a resistance R is connected in series with a blocking layercondenser K. Such a two-pole network may take the place of the blockinglayer condensers in any one of the circuits shown.

In many cases it may be desirable that the additional fixed condensersshould have similar characteristics as regards their apparent impedance,loss angle, etc., in dependence upon frequency corresponding to therespective characteristics of the blocking layer condenser for adefinite or average controlling or biasing potential. The head of theimpedance vector of a blockinglayer condenser for different frequenciestravels approximately along a circle.

In Figures 12a and 1217 there are shown substitute networks of this typeadapted for obtaining a predetermined relation between capacity and lossangle over a desired frequency range. The use of such substitutenetworks is especially advisable if the transmission characteristics orpropagation factor of the network is to be substantially independent offrequency. Thus, the substitute networks according to Figures 12a and12b may be provided in place of the impedance Z in Figures 4 and 10 oras a substitute for the condensers K1 and m in Figure '7, in place ofthe condenser C of Figure 9, or in numerous other circuit arrangements.

In the foregoing it has been shown that the coupling or propagationfactor of a network may be varied by the provision of one or moreblocking layer condensers as coupling or transmitting elementscontrolled by a potential impressed thereon either from the outside orgenerated within the circuit, such as in the form of a vari able seriescapacitance (Figure 4), a parallel circuit (Figure 10), a combination ofboth (Figure 5), or by the varying the balance of' a bridge circuit(Figures 6, 7, 8, 9). It has further been shown that both the amplituderelation between input and output potential and the mutual phaserotation between the potentials may be controlled in this manner purelyelectrically without the use of any mechanically moving parts ordevices.

The potential for controlling the coupling or propogation factor may bea relatively slowly varying potential or of rapidly varying charactersuch as an audio frequency potential or a potential of higher frequency.In the latter case the frequency (carrier frequency) impressed upon theinput terminals is modulated in accordance with the controllingpotential. The potential at the outputterminals will be amplitudemodulated if the circuit is designed in a manner so as to control theamplitude ratio in proportion to the controlling potential.Alternatively, the output potential will be phase modulated if themodulating potential eflects a phase rotation between the input andoutput potentials. If the arrangement is adjusted and balanced in such amanner that with the absence of the control potential the output iszero, a carrier suppressed modulated output will be obtained as isreadily understood. 7

In the known modulating systems utilizing rectifier-s, the modulatingeffect is due to the behavior of non-linear'resistance devices independance upon the impressed modulating or controlling potential. As isobvious a considerable current is consumed by these resistances ascompared with the inventive arrangement utilizing potential controlledcondensers which consume substantially! capacitative current only whichmay be compensated by the provision of suitable inductances inthe'manner described hereinbefore. For this reason the active powerabsorbed in the input in contrast to the known rectifier modulatingsystems is only slightly higher than the active power of the modulatedalternating current potential delivered at the output. Furthermore,comparatively low controlling or modulating potentials are required bythe invention. If the difference between the carrier frequency and themodulating frequency is substantial, the modulated output power may be amultiple of the controlling energy. This is basically not possible inthe case of the ordinary rectifier type modulating arrangements.

In view of the comparatively small controlling energy the modulationsystem described may be utilized toserve as an amplifier forintensifying weak currents or potentials. Such amplifiers utilizingpotential controlled or blocking layer condensers may therefore beappropriately termed as capacitative amplifiers in contra-distinction tothe customary vacuum tube or electron discharge amplifiers.

A two-stage amplifier construction of this type is shown in Figure 13.In the latter, an alternating potential E1 having a constant frequencysubstantially in excess of the frequency of the potential e1 to beamplified and applied to the input potential 1', s serves as the localpower source replacing the customary anode or B-supply in the standardamplifiers. The first amplifying stage comprises a pair of blockinglayer condensers K1 and K2 connected serially in like sense and acrossthe terminals as, b of the carrier or supply potential. Similarly, thesecond amplifying stage comprises a pair of blocking layer condensers K3and K4 also connected across the terminals a, b similar to thecondensers K1 and K2. The capacitative current through the blockinglayer condensers is neutralized or com pensated by an inductance I tunedto resonance with frequency of the supply potential E1 together with theaverage capacity of the blocking layer condensers. A fixed biasingpotential 80 is impressed upon the condensers K1, K2 and K3, K4 by abattery B through the upper and lower halves of the inductance I. Tothis end the opposite poles of the battery .8 are connected to innerends it and v of both halves into which the inductance I is divided,while the tap w of battery B is connected to the junction z of theblocking layer condensers K1 and K: through the input circuit terminalr, s, and an ohmic or inductive resistance R3. The tapped portions ofthe battery B are shunted by bridging condensers C3 and C4 for thealternating currents.

In this manner'a fixed biasing potential is applied to the condensers K1and K: from the tap of the battery l3 which potential determines theratio of the capacities of the condensers K1 and K2. The tap of thebattery B may be chosen in such a manner that the capacity of K1 isslightly higher than the capacity of K: if the potential e1 to beamplified is zero. Thus, a high potential drop E1 is developed across K:or bepacity ratio may be decreased by a negative control potential e1until the high frequency potential E2 at the point x becomes zero.

It is obvious that the conditions will not be changed materially if highfrequency power is derived from the point a: such as through a couplingcondenser C4, provided that the load impedance is high relative to theimpedance of the condensers K1 and K2. Moreover, the controlling energyrequired at the terminals r, s is not appreciably increased. In theexample illustrated the high frequency potential between points a and ris rectified by the aid of a rectifier comprising four rectifiers G1 toG4 arranged in a bridge circuit in a known manner whereby a lowfrequency potential e2 is impressed upon the primary of a transformer Tcorresponding exactly to the input potential e1 except for a directcurrent component. The secondary voltage e; of the transformer isincreased to a multiple of the primary voltage e11 and is also greaterthan the potential e1. The potential e3 is then further intensified bythe condensers K3 and K4 in a second amplification step by impressingthe same upon the point at between the condensers K1 and K4 through animpedance such as a resistance R4. Condensers & and K4 are biased by thebattery B by connecting the lower end of the transformer secondary T tothe tap w of the biasing battery. The amplified potential is thenimpressed upon a further rectifying system G5-Ga through a couplingcondenser C5 and the final amplified output potential e; is derived fromthe terminals 0, d for further amplification or utilization in asuitable output circuit. The output energy at the terminals 0, dis asubstantial multiple of the controlling energy impressed upon theterminals 1', s; that is, the system functions as an amplifier. As isobvious any other rectifying arrangement in place of the bridge systemsmay be employed for the purpose of the invention. The input capacity atthe terminals 1, s may be eliminated by providing a suitable substitutenetwork. If the input potential comprises a mixture of frequencies ofrelative small band width an inductance may be used for this purposeconnected in parallel to the input terminals. In place of controllingthe amplitude transmission ratio as utilized in the arrangementaccording to Figure 13 by the aid of the condensers K1 and K2 or IQandKi, respectively, any other suitable arrangement embodying potentialcontrolled condensers may be employed such as arrangements shown inFigure 4, 6 or 7. Furthermore, it is understood that the repeater ortransformer T serving for increasing the amplified potential may bedispensed with if the modulated high frequency potential is increasedbefore rectification by other suitable means such as by the aid of ahigh frequency or resonant transformer.

It will be apparent from the above that the invention is not limited tothe specific arrangements of parts and circuits shown and disclosedherein for illustration but that the underlying principle and inventivethought are susceptible of numerous variations and embodiments comingwithin the broader scope and spirit of the invention as defined in theappended claims. The specification and drawings are accordingly to beregarded in an illustrative rather than in a limiting sense.

I claim:

1. A four-pole circuit for translating oscillatory energy having aninput and an output, an aperiodic impedance network connecting saidinput and output, said network including at least one variablecapacitance element comprising fixed electrodes and a semi-conductingintermediate layer intimately united to at least one of said electrodesand adapted to block the electric current in at least one direction, andmeans for impressing a variable control voltage upon said electrodes inthe blocking direction, thereby to vary the capacitance of said elementwithin a range so as not to affect the aperiodic condition of saidnetwork to effect a corresponding control of the energy propagationfactor between said input and said output.

2. A four-pole circuit for translating oscillatory energy having aninput and an output, an aperiodic impedance network connecting saidinput and output, said network including at least one variablecapacitance element for controlling its electric propagation factor,said capacitance element comprising a pair of fixed electrodes and asemi-conducting layer therebetween intimately united to at least one ofsaid electrodes and adapted to block the electric current flow in atleast one direction, means for applying a constant biasing potential tosaid electrodes in the blocking direction, and further means forsuper-imposing a variable potential upon said biasing potential, therebyto vary the capacitance of said element within a range so as not toaffect the aperiodic condition of said network and to .efiect acorresponding control of the transmitting properties of said network.

3. A four-pole circuit for oscillatory energy having an input and anoutput, an aperiodic impedance network comprising ohmic and capacitativeimpedance elements connecting said input and output, at least oneimpedance element of said network being constituted by a variablecapacitance element adapted to control the phase relation between energybeing translated by said circuit, said capacitance element comprising apair of fixed electrodes and a thin semi-conducting layer therebetweenbeing intimately united with at least one of the electrodes and adaptedto block the electric current in at least one direction, and means forimpressing a variable control voltage upon said electrodes in thecurrent blocking direction to vary the capacitance of said elementwithin a range so as not to affect the aperiodic condition of saidnetwork.

4. A four-pole circuit for translating oscillatory energy having aninput and an output, an aperiodic impedance network comprising ohmic andcapacitative impedance elements connecting said input and output, atleast one impedance element of said network being constituted by avariable capacitance element adapted to control the phase relationbetween the energy being translated through said network, saidcapacitance element comprising a pair of fixed electrodes and a thinsemi-conducting layer therebetween being intimately united to at leastone of the electrodes and adapted to block the electric current in atleast one direction, means for impressing a steady biasing voltage uponsaid electrodes in the blocking direction, and further means forsuper-imposing a variable control voltage upon said biasing voltage tovary the electrical capacitance of said element within a range so as notto afl'ect the aperiodic condition of said network.

5. In a system as claimed in claim 1 wherein said network constitutes apotentiometer circuit with said variable capacitance element forming apart thereof.

6. In a system as claimed in claim 1 wherein said network constitutes abridge circuit with said capacitance element adapted to control thebalance of said bridge.

7. In a system as claimed in claim 1 wherein said controlling potentialis supplied from a separate source and impressed from the outside ofsaid network upon said capacitance element.

8. An electric wave translation circuit having an input and an output, apair of capacitance elements each comprising a first electrode, a thinsemi-conducting layer intimately united to said electrode and a secondelectrode in electrical contact with said semi-conducting layer to blockthe electric current flow in at least one direction betweensaidelectrodes, said capacitance elements being serially connected inthe same 1 sense and coupled to said input, said output being coupled toone of said condensers, a direct potential source connected across saidcondensers, a tap connection from an intermediate point 01 said sourceto the junction of said elements to variably and diflerentially biassaid elements in their blocking directions. means for blocking waveenergy being translated from said potential source, and further meansfor blocking the direct potential of said source from said input andoutput.

9. In a circuit as claimed in claim 8, means for introducing anadditional varying control voltage in the pathbetween said tap and thejunction of said capacitance elements.

10. In a circuit as claimed in claim 8, a current blocking impedancepermeable to direct current being arranged in the path between said tapand the junction of said capacitance elements.

11. In a circuit as claimed in claim 8 wherein the input potential issupplied by a source of substantially constant alternating current,

-means for superimposing a varying control voltage of relatively lowfrequency upon said biasing voltage, and rectifying means connected tosaid output.

GUSTAVE GUANEILA.

